Key is to pay attention to your knock retard given your gas. On a true 93 octane / 98 Ron it should be able to run 21psi and taper off with very little knock retard, if any.

I only have AMS IC's + Exhaust + tune with none of the other stuff, trap 133ish on vbox in the 1/4 on 98Ron with basically 0 knock retard when ambient temps are at 20-25 degrees Celsius.

 

Yes I was. On the phone with him last night...his answer was ...that there are 25 diffrent ways to tune your car...some people just add boost to get power ..on my tune (btw 18.5 ) was my boost I was wrong on the number..he not only tunes the turbo boost side but he tunes the motor also....he also said if people like running that high on stock turbos they cause a lot of heat....so he would doubt that those numbers would hold up long..

 

Your tuner sounds like he knows exactly what he's doing - good stuff - i'm seeing a few horror stories on these boards from over tuned cars. Sad thing is people who are new to 997 turbo onward Porsches don't even realise they're killing their $50,000 Mezger masterpieces with very average tunes running way too much boost - ticking (wallet sapping) time bombs

The other thing is when something goes wrong because the turbo is running more boost than a space shuttle the tuner takes no responsibility whatsoever - I'm sad to say that a few owners are learning the hard way that running crazy amounts of boost on stock 997.1 OEM or hybrid 997.1 VTGS is a fallacy - IATs and EGTs go out of control - I know of two guys here in the UK that have recently had to have full $40,000 rebuilds due to running very poor off the shelf tunes on 997.1 turbo

 

Yes trust what he says. Very true. Pushing those stock turbos much further without at least a comp wheel upgrade and only results in heat and eventually a busted shaft due to over speed. Upgrade the wheel if you want more power at a fairly reasonable cost.

 

Good explanation. Been there done that, at the track.

Heat is the worse mod enemy for our stock VTG setup.

 

YES! Well said!!

 

I have a full Bolt on car....every Bolton you can think of...3 inch exaust with headers 82 mm plenum ams y pipe turbo inlet piping running cobb custom tune....withe all the air there ..and all the air being able to exit....what boost pressure should these stock turbos be pumping....I tend be be a tad bit on the aggressive side..

 

"AWE exhaust, Cobb AP, GT2 ICs, ID 1k injectors, do88.se turbo inlet pipes, 764 pressure plate, H&R, BBS CH-R. 5.9 60-130, E85/stock VTGs (PTF mapping). Now RobTuned with 656 whp / 693 wtq."




Im about to buy an 08 TT and gonna do your same mods to hopefully hit the 650+whp too

 

I would not say your running aggressive with the mods you have. Big thing is heat/efficiency and how much yield you get per pound of boost. that obviously depends on many factors so a good threshold point seems to be 18-20lbs for stock wheel VGT. Could they "push" more boost, yes. But the yield tends to fall off and then its just ware and tear from there. There is only so much LBS of air that stock wheel can produce before it becomes inefficient.

 

Are you being theoretical or are you saying this from looking at data from tuning the VTG? I know you did a bunch of work on VTGs before so I'm curious what kinds of boost it likes before it runs out of efficiency, and what kinds of EGTs you see etc

 

Crank up the boost boys what could possibly go wrong

 

From testing we seen in live data. Again though there are still variables but in all reality, its pretty close. As EGT is more defined in Air fuel mixture, a mix of turbo back pressure, RPM, and simply yield per pound was monitored to come to this number. Though I would love to have some actual Turbo Speed sensor data to really confirm. But this is what we have seen in the past if your talking using a safe threshold of 80-90% duty. And of course it really starts to fall off as RPM climbs. Your TQ curve will show this without any data at all.

 

The factory VTGs work quite well at 22 psi as well, and gain about the standard amount of power per lb of boost as would be expected going from 20 to 22. My IATs are very much in check with standard 997.2 intercoolers.

Here is a run through all of second, third, and 4th gear on pump gas. Notice the boost pressure and RPM. My IATs at the start of the pull were 76 degrees. Final temp is 104 for the sake of rounding. Ambient temp was in the 60s.

This map is good for 60-130 times of 6.7 seconds.

 

What are your EGTs on that pull?

 

Usage environment means everything.

I could use my stock VTGS at 22psi on occasion with no issue. Head to the track and see how easily they fail.

I'm with John on this debate.